Tube-rolling.



R. U. STIEFEL.

TUBE ROLLING.

APPLICATION FILED NOV. 12, 1909.

88,884. Patented Apr. 4, 1911.

SHEETSSHEET 1.

R. O. STIEFEL.

TUBE ROLLING.

APPLIGATION FILED NOV. 12, 1909.

L. 2 9 m 4% my Am d 8 t n ,w a P mtgmagiumq b v R. C. STIEFEL.

TUBE ROLLING.

APPLIGATION FILED NOV. 12, 1909 Patented Apr. 4, 1911.

4 SHEETS-SHEET 3.

R. G. STIEFEL.

TUBE ROLLING.

APPLICATION FILED NOV. 12. 1909.

. 988 834 Patented Apr. 4, 1911.

4 SHEETSSHEET 4.

I ullll ,r

Qwi Mwooco: 4 vwe W606 $31 M Gttozmmgo UNITED STATES PATENT OFFICE.

BALPH CHARLES STIEFEL, 0F ELLWOOD CITY, PENNSYLVANIA, ASSIGNOB TO THE' SHELBY STEEL TUBE COMPANY, OF PITTSBURG, FENNSYLVANIA, A CORPORATION OF NEW JERSEY.

TUBE-ROLLING.

Specification of Letters Patent. Patented Apr, 4, 1911,

Application filed November 12, 1909. Serial No. 527,640.

City,'Pennsylvania, have invented certain new and useful Improvements in Tube-Rolling, of which the following is a specification, accompanied by drawings exemplifying the invention in certain pre erred forms.

In the drawings Figure lis a diagram-- matic view of instrumentalities for carrying out the process in one form. .Figs. 2, 3 and 4 are cross sections of'tubular blanks showing the effect of different grooved'rolls for longitudinal rolling. Fig. 5 is alongitudinal section through the cross rolling bodies or disks of Fig. 1. Fig. 6 is a cross section ,on the line 6-6 of Fig. 5; Fig. 7 is a diagram of some ofthe motions involved. Figs. 8 and 9-are details showing modifications of Fig. 1. Figs. 10 and 11 are longitudinal sections on planes perpendicular to each other, showing the substitution of rolls for the disks of Fig. 1. Fig. 12 shows-in longitudinal section a modified use of disks.

The invention relates to the art of rolling tubes and tubular blanks rapidly in a continuous process.

The object of the invention is to effect the rolling out of a tubular blank upon a man-. drel in a most expeditious manner and preferably to accomplish substantially the entire reduction required of the tubular blank by a few sets of rolls and to produce a tube of substantially true circular shape delivered loose upon the mandrel bar.

In one operation of continuous tube roll- I ing 'mills known in the art, Where a long mandrel bar is inserted into theheated tubular blank or billet and the said blank, in unison with the mandrel bar, is'passed through a series of-sets of rolls with consecutively smaller grooves, it has been customary to use a tubular blank of an insidediameter somediameter occurs in such case before any substantial reduction of thickness of wall can commence. The accomplishment of said reduction ofdiameter, together with the total reduction required of the wall of the blank, necessitates vnaturally a greater number of roll pairs than would be required if-the blank tightly embraced the mandrel bar'before the two passed through the rolls.

-Also, in the operation of such continuous mills, it has been customary to arrange the grooves of some of the rolls to produce a 1 tube of pronounced oval shape only partlyin contact with and adhering to the mandrel bar, facilitating the flow of the metal on the mandrel bar between said rolls by employing oval grooves and also facilitating the withdrawal of the mandrel bar from the'tubes,

In this manner a tube of non-circular shape is produced by the continuous mill process, sa1d tube requiring further subsequent manipulation to give it a regular and true circular contour.

By the present invention in its preferred form I am able to overcome the disadvantages pointed outin the two preceding paragraphs.

I show in Fig. 1, partly in side elevation and partly in section, a cylinder a in which, by means of a suitable fluid, a plunger or piston Z) with a hollow body or piston rod 0 is caused to move back and forth at will; a mandrel bar at inserted in the hollow piston rod 0, a tubular blank 6 resting on a support f and prevented from moving in the direction of the arrow by a disappearing stop 9 which is slotted large enough to allow the mandrelbar d to pass through, but too small to afford a passage for the blank 6; a series 72. of sets or pairs of rolls with consecutively smaller grooves, said grooves being of pronounced oval or widened shape, as presently explained, in all the rolls; and a pair of rotary bodies k'arranged to act on the tubular bl'ankalong one converging, one parallel, and one diverging portion, as in Fig. 5.

The operation is as follows: A tubular blank 6 with an inside diameter slightly smaller-than or approximately equal. to the diameter of the mandrel bar d is placed on its support f in front of the now raised stop The mandrel bar d is placed behind the tubular blank 6, the hollow piston rod 0 being approximately at the end of its back stroke, and is wholly or partly inserted into the piston rod 0 or so guided that said piston rod on its forward stroke receives it'in its forward and the projecting mandrel bar .is

forced into the tubular blanke, causing the blank either to embrace tightly the mandrel bar if the inside diameter of the tubular blank, as is preferable, is slightly smaller than the diameter of the mandrel bar, or to closely fit around the mandrel bar with ap-- proximately no space between the bar and the inside surface of the .blank if the inside diameter of the tubular blank is approximately equal to the diameter of the mandrel bar. It is evident that, in forcing the mandrel bar 03 through the tubular blank the bar will have to sustain a thrust whose tendency is to buckle or bend the bar, especially if a long mandrel bar of small diameter has to be used, as in rolling long tubes of small in.- side diameter. The ob ect of the hollow piston rod 0 is, therefore, to form a side support for the slender mandrel bar at this stage of the operation, preventing the buckling of the bar under the load. The forward stroke of the piston is continued until the mandrel bar projects through the tubular blank 0 a suflicient distance to allow for the elongation of the tube upon it. The stop 9 is now withdrawn and the'mandrel'bar d and the tubular blank e move in unison with the piston toward the rods it until within the grip of the first pair of said;

rolls, which will thereupon cause the blank and bar to pass through and be reduced between the series of sets or pairs of rolls h and 70. When the tubular blank and the mandrel bar have been gripped by the first pair the mission of the hollow piston rod is fulfilled and itmay be brought back to its starting position, ready for the next tubular blank or billet.

' In Fig. 1, the pushing, and supportin member 0 is shown as a piston rod, operate in connection with a piston '72 and a cylinder a; but other mechamcal means for causing said pushing and supporting member to move back and forth could be employed without affecting my invention.

The aforementioneddistance that the mandrel bar 03 should project through the,

tubular blank or billet e at the time the stop g is withdrawn, depends upon the following conditions :.The velocity of rotation of each individual set or pair of rolls in the roll combination h is timed according to the reduction made in each pass in the tubular blank between the rolls and the mandrel bar, the metal, of course, leaving each pass at a velocity determined largely by the rotation of each set or pair of rolls and increasing with each consecutive set or pair in proportion to the reduction of the cross section of the tubular blank. However, it is evident that, although the mandrel bar is tightly between t-herolls of the continuous ro gripped by the rolls, in the action of the rol billet, it can not itself assume the several velocities of the tube in each of theconsecutive passes, but will be given a velocity that is approxlmately an average of the sevs on the wall of the tubular blank or eral metal velocities. 'This causes thetubwor billet. As now the working of .the wall of the tubular blank or billet takes sets it, the rotary bodies 70, and the mandrel bar d,

the latter must also project so far forward of the tubular blank 6 that .no part of. the

metal of the tubular blank or billet will advance beyond the end of the mandrel bar at the time they reach the last-Working point, the rotary bodies is. If these rotary bodies are placed very close to the continuous roll lace sets-h, the metal may advance ahead of the mandrel bar beyond thev pass formed by said rotary bodiesand a partial stripping take place. But in case these rotary bodies are placed sofar away from the continuous *roll sets it that the tubular billet is nearly free from the last pair of rolls of said continuous roll sets before entering the pass formed by the rotary bodies is, the mandrel bar should project through the tubular blank or billet e a sufiicient distance at the time of withdrawing the stop 9 to insure that the tubular blank or billet will not be partly stripped off the mandrel bar in passing through the continuous roll sets It, previcus to'being worked in the pass of the rotary bodies is. i

-It is evident "that as the tubular blank e tightly embraces the mandrel hard, the re-' V duction in thickness of wall'commences in thefirst pair of the consecutive sets of r0 s, thereby reducing the necessa number of sets 0 rolls or passes require fora given reduction of wall thickness. As the round-.

ing of the tube takes place in the pass formed by the rotary bodies 70, no attempt need be made to round the tubein the con-.

tinuous roll sets h, so that all passes in these continuous roll sets It can thus be made widened oroval and so facilitate an equally free flow of the metal'of the tubular blank or billet upon the mandrel bar in all the rolls, in two. directions, crosswise as well as lengthwise.

Fig; 2 shows longitudinally ofthe pass,

the acting portions of one set or pair of rolls dot the continuous roll sets. The mandrel wall, as shown by the dotted section, pressed tions 3 of the arriving section will be bar (1 and the blank 0 are in cross section. The section in dottedlines shows the section of the tubular blank leaving the preceding pair of rolls which, as shown in. Fig. 1, have their axes perpendicularto the axes of hi roll pair h. The full drawn section of he ubular blank is the section after having been worked in the pass of the roll air It. The tubular blank reaches said roll pan with he thinnest, or reduced, portions of its down onto the mandrel bar in line with points t by the reduction in the previous pass, The thickest portions at t are standmg off from the mandrel bar d in consequence of the crosswise flow of the metal on the bar in the preceding pass. In passing through the roll pair h, the thicker porpressed ddwn along the major axis of such sect-ion onto the mandrel bar and its thickness reduced till it becomes the thinnest at t, the metal-fiowing both crosswise and lengthwise. This crosswise flow of the metal from 15, together with the reversing of the major and minor axes of thearriving and the resulting oval, will naturally cause the metal at the thicker part of the section, or along the new major axis, to stand off from the mandrel bar at If an amount depending on the reduction taken and the previous periphery or degree of ovality of the arriving section. This ovality, w1th its resulting clearance between the wall of the tubular blank and the mandrel bar for a certain portion of the circumference of the mandrel bar, naturally allows a comparatively free and unrestricted flow of the metal crosswise and more so than should the metal embrace the whole or nearly the whole of the circumference of the mandrel bar as would be the case if a circular roll-groove were used. It also likewise allows a freer flow of the metal lengthwise, as only part of the circumference of the mandrel bar is in contact with the wall of the tubular blank, reducing only a portion thereof. This permits of an easier adjustment of the relative velocities of the mandrel bar and the metal referred to above with a consequent decrease in wear of acting surfaces and in power consumption. This crosswise flow of the metal, if unrestricted, would give a clearance between the mandrel bar and the inside of the tubular blank constantly increasing from pass to pass becoming greater than desirable. By

properly proportioning the ovalit-y of each time effecting a true circular sha 3 shows this finning feature under such conditions, showing in dotted outline the metal arriving from the preceding pair of rolls,

and the full drawn section e the result of the narrow or restricted pass, producing the fins at a by squeezing the metalout between the collars or flanges of the rolls.

that if any of the asses of the roll sets are circular, as shown in Fig. &, the tendency to As the tubular blank or billet is passing through the last pair or set of rolls of the continuous .roll sets, Fig. 1, it enters into the pass formed by the rotary bodies is placed immediately following and in close proximity. Thus the tubular blank with the accompanying mandrel bar, when entering and being worked upon by the rotary bodies is, is still in the grip of part or of all of the sets or pairs of rolls constituting the continuous roll sets. The rotary bodies is form a pass embracing the tubular blank or now partly finished tube along longitudinal lines. They are revolved at rates corresponding to the flow and advance of the metal from the con tinuous roll sets, thereby crossrolling or rounding the wall of the billet. of the rotary bodies imparts to the metal a forward and'a rotary motion, at the same of the tube. This rolling of the wall 0 the tube in the pass formed by the said rotary bodies and on the mandrel bar, also results in a slightlylarger inside diameter of tube than the diameter of the mandrel bar, thus facilitating the subsequent removal of the bar. The pass formed by therotary bodies in consists of a converging, a parallel, and a di-. verging exit portion, the converging portion of the pass forming the inlet for the metal to be rolled and providing a gradual approach to the point of contact. The parallel portion of the pass is formed by what could be called the main working surfaces of the rotary bodies, the converging portion of the pass changing into the parallel portion at a point where the distance between the surfaces of the two rotary bodies, measured diametrically across the axis of the tube and The action' It is clear pass and perpendicular to the acting surfaces of t e rolls is slightly smaller than the minor axis of the oval section of the tube arriving from the continuous roll sets h.

Fig. 5 is a horizontal sectional view of the rolling bodies is, the section being taken in .a plane through the axis of the tube or pass and parallel to the axes of rotation of the rotary bodies is, showing in section the ro- The direction of advance of the tube and mandrel bar is indicated by the arrow. En-

tary bodies andthe tubular blank or tube -e, and in full-view the-mandrel bar (Z.

positions of this section possible, relative to.

the width of the pass formed by the rotary bodies, one with the, minor axis of said oval section in the sectional plane of Fig. 5 on plane 5'5 of Fig. 6; the other with the ma-' jor axis,- in such plane. It is evident that an infinite number of intermediate positions between these two limits are possible. In the first position, which is preferred, a reduction of wall against the bar takes place immediately as the metal is gripped by the surface of the rotary bodies 70 la, the distance between those portions of the surfaces of the rotary bodies that form the parallel portion of the pass being slightly-smaller than the minor axis of aforesaid oval section, 71. a. smaller than the sum ofthe diameter of the mandrel bar and twice the minor thickness of the wall of the tube on leaving the last, continuous roll set h. In the second extreme position the tube will likewise be given a rotary motion as soon as in contact with the surfaces of the rotary bodies 'whichwill occur smoewhat sooner owing to the greater length of the major axis, but the wall will not however be compressed against the bar by said rotary bodies until the tube has advanced at least to a point where the distance between the surfaces of the rotary bodies, does notexceed the diameter of the bar plus twice the major thickness of the tube on the major axis.

Fig. 6 is a sectional view looking forward, the section being taken ona plane 66 of Fig. 5, perpendicular; to the axis of the I blank or tube through the parallel portion entering portion of the of the pass formed by the rotary bodies k is, showing part of said rotary bOdlGS, the 'tubu lar blank or tube 6 and the mandrel bar d. The arrows show the direction of rotation of the bodies involved. In the converging ass, the tube is gradually but slightly re need in thickness until it enters the parallel portion of the pass, where the wall is rolled between the surfaces of the rotary bodies and the mandrel bar on the parallel contact lines, much in the manner of rolling a plate, although in thiscase 'an endless one. This arallel portion of the pass should thus finish the work of reducing the metal to a uniform'thickness, started in the converging portion, and it also smooths the wall. It is evident that during this part of the process the tube ifreduced to ur form thickness assumes the oval or elliptical shape shown in Fig. 6, the minor axis of the section reaching its min-imum therein as seen from-Figs. 5 and 6, the major axis being perpendicular thereto and the periphery bemggreater than on first entering the-pass of these bodies. This major axis has naturally always the same.

position at the section 6-6 relative to the rotary bodies 7c is, the metal of the tube all the time revolvin relatively to such axis in the direction of t earrows shown in Fig. 6.

reduction of the wall thickness, and the wallhaving moved away from the harm becomingvcircular. ith the arran ment shown in- Fig. 1, where the rotary odies k k are placed in close proximity to the continuous roll sets, the tubular blank or tube and the mandrel bar are still in the grip ofall or'some of the -airs of the continuous roll sets h when the dies IO/6 come in to action. The rotary motion is thus imparted only to the metal of the tube and particularly 'to that portion of same that is free from the grip of the rolls of the continuous roll sets It. The mandrel bar cannot rotate in the grip of the-rolls of the continuous roll set h. On the other hand, the forward motion of the metal imparted by the rotary bodies should be determined by thev velocity with which the metal isleaving the continuous rolls k and is to be governed thereby. During the greater part of the cross rolling by the ropass formed by said rotary bodieswith endwise motion only, both the metal and the mandrel bar being still in the grip of the rolls of the continuous roll sets It.

As the metal and the mandrel bar are delivered to the rotary bodies It with endwise motion only, the cross rolling action of the bodies necessarily produces a twist rotary g of the metal of the tube as Wlll be. seen approximately by referring to the dlagram 7. Fig. 7 shows in diagram the outline of the rotary,-disk-shaped bodies is I: and the axis 'z z of the tube and mandrel bar, an arrow indicating the direction of the end: wise motion of the metal and bar, and two arrows giving the corresponding directions of rotation of the rotary bodies. Let 01' be a perpendicular-or radius from the axis 0 to the pass axis z-z. Let I) represent the point of first contact, and b m the surface velocity of the rotary bodies at 6. Then I; U will represent the component of endwise velocity and b w the component of crosswise or rotary velocity at 7). Further let a represent the point of last contact, ande p the velocity of the rotary bodies at said point. As before, 0 m and c y representrespectively the velocities of endwise andof rotary motion at said point 0. The surface velocity increases in proportion to the respective radial distances 0 r, 0 b, 0 0, etc. from the axis of rotation. This velocity, as 0 p, at any point,- as 0, is proportional to its radius as 0. c. It is measured by the radius, multiplied by the. constant angular velocity of the roll. Let j bethe angle of divergence between the direction of motion 'as for example c p and the line of the pass, being the then the feed is approximately uniform and the rotative tendency progressively faster, but the twist is somewhat lessened by slip and by increased periphery of the tube wall compared to the mandrel. slip in addition to facilitating the smoothing action are a known benefit in certain type of tubes as where peripheral strength to resist pressure is desired. The metal is rolled obliquely forward in relation to the axis of the tube. It is also evident that a tendency to a similar twist of the metal is produced between the last pair of continuous roll sets it and the point of first contact =b between therotary bodies 7c and the metal. This twist, however, is slight in proportion as the point of first contact is near point 1', and is m'l approximately when thetwo coincide, the rotary bodies imparting endwise motion only to the tube at that point.' However, the

twist of the metal between the last pair of rolls 7:; and the pass of the rotary bodies k 70 can be distributed over a longer distance and it can be eliminated altogether by arranging the last pair of rolls h obliquely relative to each other, the metal in this case beingde livered to the rotary bodies is k with the same obliquity as at point of first contact between the rotary bodies and the metal. This, however, does not impart to the mandrel bar a rotary motion, except in the last moments only, when the mandrel bar is in the grip of only the last pair of rolls. The mandrel bar during the greater part of the rolling is in the grip of all or of several of the roll pairs of the-continuous roll sets h. In this case the distinctive features determining the rolling conditions are-"that the mandrel bar enters into the pass formed by the rotary bodies la 70 with only endwise motion,

The twist and.

while the metal enters said pass with both endwise and crosswise or rotary motion. Rig.

8 shows in side elevation the continuous roll sets It with the last pair of rolls arranged obliquely as just described and the rotary bodies 70 k placed in close proximity to the last continuous roll set it.

Instead of having only the last pair of rolls of the continuous roll sets 7t arranged with oblique axes, all the pairs of rolls may be thus arranged. Fig. 9 shows this arrangement, h representing the rolls with axes arranged obliquely, and 7c 70 representmetal to the rotary bodies 70 7a with the obliquity and rotation corresponding to thefirst contact between said rotary bodies and the metal. The obliquity or the setting of the successive pairs of rolls h should be such as to turn or deliver the metal of the tubular blank or billet to the next pair with a quarter turn in the distance between two consecutive roll pairs or otherwise so as to properly present the major axis to the rolls as already explained. In this case the distinctive features determining the rolling conditions are that both the metal and the mandrel bar enter into the pass formed by the rotary bodies is with endwise and with crosswise or rotary motion. It is evident that in this case the twist of the metal of the tube, previously mentioned as taking place between the last pair of continuous rolls h and the rotary bodies, is eliminated. The rotary bodies 70 is can also be placed at sufficient distance from the continuous roll sets to allow the metal and the mandrel bar 'to become eithercompletely ornearly free from the continuous rolls sets before enter- It will be seen that the form of rotary bodies or disks 7c is can be replaced by a set of cross rolls or rotary bodies with axes oblique to the pass axis and of a contour such as to form a narrow band or line contact between the surface of the roll and the metal to be rolled, constituting the parallel portion of the pass, and to form a converging approach to the above line contact and subsequent diverging surfaces effecting a gradual release of the grip of the rolls. Fig. 10 shows in sectional plan (or side elevation) and Fig. 11 in direction at right angle thereto a pair of such cross rolls'with oblique axes,-a mandrel bar (I and a tubular blank or tube 6. The arrow indicates direcroll is a rotary body of comparatively uniform diameter, the greatest variation being in the converging and diverging portions of. the pass. The parallel portion; of the pass is formed by the central portion of the rolls having a slightly concave hyperboloidal longitudinal contour, .as will be well understood.

As, from practical reasons the obliquity Q of the rolls is generally comparatively small and the length of the arallel portion of the pass or the hyperboloi a1 portion of the rolls -comparatively short, it is evident. that the theoretically proper variation of diameters, and the consequent difference in respect to twist is rather insignificant. The greatest variation occurs in the-convergin and diverging portions of the pass; but t is variation is balanced by shortness of contact and light, pressure, permitting slip. 1 Summarizing the different ways described for cross-rolling the tubular blank or tube on leaving the continuous roll sets h, we have the followin In Fig. 150th the metal and the mandrel bar enter into the pass formed by the rotary bodies is with endwise motion only, both the metal and the mandrel bar being in the grip of the rolls of the continuous roll set it; producing pronounced twist of the metal of the tube within the pass ofthe rotary bodies k and slight to no twist between the last pair of rolls of the continuous roll set It, and the rotary bodies k.

In Fig. 8, the mandrel bar enters into the I pass formed by the rotary bodies It with only endwlse motion, but the metal with both endwise and crosswise or rotary. motion, we have nearly the same conditions between the contact lines of rotary bodies is, but the metal is delivered obliquel to these rotary bodies and with same obliquity as that in efi'ect at the, point of first contact between the rotary bodies k and'the metal of the tube. We have twist by the last pair of rolls h.

In Fig. 9 both the metal and the mandrel bar enter the pass formed by the rotary bodies is with both endwise and crosswise or rotary motion and we have substantially the same conditions as in Figs. 1 and 9 between the contact lines of rotary bodies is, but no twist back of point of their first cont-act. If the rotary bodies is be placed at 'sufiicient distance from the continuous roll sets to allow the metal and the mandrel bar to leave the rolls of the continuous roll set before conrotary bodies in, then while still having pro nounced twist between the contact lines of the rotary bodies k we get no twist back of point of their'first contact. If instead of the disk-like rolls kin-the last instance we employ the rolls of Fig. 10,. we} have materially p reduced twist'between contact lines of the cross rolls and no: twist back of point of first contact.

Instead of forcing the mandrel bar into the tubular blank as shown in Fig. 1 and described'in connection therewith, the tubular blank can be caused to close around the man drel bar with ap roximately no space between the'bar and the inside surface of the tubular blank or billet, bypassing the tw0. in unison with each other through a pair of rotary bodies.

These rotary bodies, being substantially the same as the rotary bodies 7c previously described, should be placed so that the tubular blank or billet with the mandrel bar are entirely. freed from their grip before they enter the rolls of the continuous roll set. 72.. Fig..12 is a sectional view, the section being taken in 'a' plane through the axis of the tubular blank or billet e and parallel to the axes of rotation of the rotary bodies 70, showing the rotary bodies, the tubular blank or billet, and the mandrel bar (1. The direction of advance of the blank and the mandrel -bar'is indicated by the arrow. The tubular blank with the mandrel barin the correct relative position as previously described, are caused to enter the pass formed by the rotary bodies. When contact between the metal of the blankand the surface of the rotary bodiesoccurs-in the converging portion-of the pass, the metal is gripped by said rotary bodies and a rotary and a forward V motion imparted to same. This rotary and forward motion exposes the whole circumference of the blank to the pressure. of the rotary bodies and advances the blank into the contracted portion of the pass, gradually reducing the diameter of the blankand at the same time somewhat increasing the thickness of the wall. Thus the tubular blank is closed around the mandrel bar with approximately no space bej tween the blank and the mandrelbar if the opening of the parallel portion of the pass is such that the wall of the tubular blank is not pressed appreciably against the mandrel bar d. Should by mistake the position of the rotary bodies have been so adjusted that the converging opening be such that the wall of the billet would be under considerable pressure between the rotary bodies andthe mandrel bar, then an expansion of: the billet in the parallel portion of the passwould re-- The rolling conditions when closing the tubular blank aroundthe mandrel bar by means of rotarybodies, are substantially as previously described with reference to Fig. 7. The diverging portion of the pass formed by the rotary bodies, performs in this case no other function than permitting an easierexit of the metal with less risk of marking the surface of the blank than would be the case if the pass terminated abruptly with the parallel portion.

By grooves wider than concentric with the bar it will be understood that I compare the grooves with grooves of any given depth that are concentric with the bar and mean that the grooves are relatively flatter and wider than such concentric groove would be.

What I claim is V i 1. In the art of rolling tubes, the improvement consisting in forcing a billet or tube tightly upon a mandrel bar, then longitudinally rolling the tube on the bar between successive pairs of longitudinally acting rolls having grooves wider than concentric to the bar and which do not completely touch and confine the tube but act along limited paths, leaving it free to flow transversely as well as longitudinally, the successive pairs acting along different lines or paths along the surface of the tube, and then cross rolling the tube between cross-rolling bodies having rolling surfaces first convergent then substantially parallel with the bar and then divergent, whereby the tube wall is rendered substantially of uniform thickness and smooth and circular, and is loosened from the mandrel bar.

' 2. In the art of rolling tubes, the improvement consisting in forcing a billet or tube tightly upon a mandrel bar, then longitudinally rolling the tube on the bar between successive pairs of longitudinally acting rolls having grooves wider than concentric to the bar and which do notcompletely touch and confine the tube but act along limited paths, leaving it free to flow transversely as well as longitudinally, the successive pairs acting along different lines or paths along the surface of the tube and then cross-rolling the tube on the bar between cross-rolling bodies having surfaces providing a compressive portion and a slightly divergent exit portion of the pass, whereby the tube is rolled between the bar and the crossrolling surfaces and then between the rolls onl In the art of rolling tubes, the improvement consisting in forcing a billet or tube tightly upon a mandrel bar, then longitudinally rolling the tube on the bar between successive pairs of longitudinally acting rolls having grooves wider than concentric to the bar and which do not completely touchand confine the tube but act along limited paths, leaving it free to flow then transversely as well as longitudinally, the successive pairs acting along different lines or paths along the surface of the tube and cross-rolling between cross-rolling bodies.

4. Elongating and thinning the walls of tubes on a mandrel bar by longitudinally rolling a tube and bar in a plurality of successive sets of grooved rolls while allowing the metal freedom to flow transversely, and by cross-rolling the tube bet-ween suitable rolls while the bar is still under the grip of some of the grooved rolls, and thereby twisting the wall of the tube relatively to the bar and smoothing and rounding the tube.

5. Improvementin the art of rolling tubes which comprises passing a hollow billet or tube upon a mandrel bar between grooved longitudinally acting rolls and then between cross rolls and com ressing and confining it while between the rst said rolls only along lines or paths of substantially limited width allowing the metal to flow transversely during its elongation onthe bar.

6. In tube rolling, the improvement comprising subjecting a tubular body of oval section upon a mandrel bar of circular section and diameter approximately equal to the minor internal axis of said body to the action of cross rolling surfaces forming a pass and having transverse surface speeds that differ effectively from that allowed or imparted to the bar and thereby rolling out the wall thickness to a uniform one between the bar and the bodies and rounding the tube between gently diverging portions of said surfaces.

7. In tube rolling, the improvement comsection upon a mandrel bar of circular section and diameter approximately equal to the minor internal axis of said body to the action of cross rolling surfaces forming a pass and having transverse surface speeds that differ effectively from that allowed or imparted to the-bar and thereby rolling out the wall thickness to a uniform one between the bar and the bodies.

8. In tube rolling, the improvement comprising subjecting a tubular body of oval section upon a mandrel bar of circular section and diameter approximately equal to the minor internal axis of said body to the action of cross rolling surfaces forming a pass and having transverse surface speeds that vary progressively, causing twist of the tube, and preventing or restricting the rotation of the mandrel .bar under such action while rolling out the tube wall transversely and unifying its'thickness, and then foundingthe tubular Wall between gently divergent parts of said rolling surfaces.

9. In tube rolling, the improvement comsection upon a mandrel bar of circular secprising subjecting a tubular body of oval tion and diameter approximately equal to the minor internal axis of said body to the action of cross rolling surfaces forminga' pass and having transverse surface speeds that vary progressively, causing twist. of the tube, and preventing or restricting the rotation of the mandrel bar under such action while rolling out the'tube wall transversely and unifying its thickness.

10. In tube rolling, the improvement comprising fitting the blank or tube snu 1y onto a mandrel bar and then longitudna ly rolling the metal into oval sections upon a bar and alternately converting major into minor axes and major thickness into minor thickness and then in the same heat and .travel cross rolling the tube on the bar by first converting it to uniform thickness and elliptical section on the bar, and then between diverging surfaces rolling it ,to a,

round section loose upon the bar;

l1. In tube. rolling, the improvement comprising longitudinally rolling the metal into oval sections upon a bar and alternately converting major into minor axes and major thickness into minor thickness and then cross-rolling the tube on the bar by first converting it to uniform thickness and elliptical section on the bar'and then between diverging surfaces rolling it to a round section.

12. The method of rollingtubes consisting in 'plac' a hollow'metal billet or tube upon a man rel'and elongating and reduc-g ing the tube upon the man e1 between grooved longitudinally acting rolls, and

then passing the tube and mandrel-between cross-rolling bodies and loosening the tube on the mandrelby the cross-rolllng action of said bodies;

13. The method of rolling tubes consisting in placing a hollow metal billet ,or tube upon a mandrel and elongating and reducing the tube upon the mandrel between.

grooved longitudinally acting rolls, and

then passing the tube and mandrel between cross-rolling bodies'and loosening the tube on the mandrel and rounding the successively loosened portions between diverging portions 'of'the cross-rolling bodies. 7 v 14. The method of forming tubes consisting in rolling a heated hollow billet or tube upon a mandrel to reduce its cross sec- 

